Technical Field
The present invention relates to an on-board network system having a relay device that relays communication frames between on-board networks, and between an on-board network and an external device.
Description of the Related Art
Conventionally, numerous electronic control units (ECUs) are mounted in a vehicle to control on-board devices. A plurality of on-board networks are constructed by each ECU being disposed on any of a plurality of communication buses. A relay device is connected to the plurality of communication buses to enable the ECUs to transmit and receive communication frames even between on-board networks.
In addition, in general, the communication frame includes a message and a message identifier. The message indicates various detection values indicating the state of the vehicle, commands issued to another ECU, and the like. The message identifier is used to identify the type of message. Each ECU judges whether or not to receive a message based on the message identifier in the communication frame.
In a configuration such as this, the relay device has a plurality of communication ports for transmitting and receiving communication frames. The relay device also stores therein a routing table in which the message identifier is associated with a port identifier (identifier for identifying the communication port that is the output destination of the communication frame). The relay device determines the communication port that is the output destination based on the message identifier in the communication frame (refer, for example, to JP-A-2008-99014).
When an ECU diagnosis is performed, an external device, such as a failure diagnosis device, provided in a repair shop or the like is used. This type of failure diagnosis device is ordinarily connected by wire to a connector (and ultimately the communication port) provided in a vehicle in the repair shop or the like. As a result, the failure diagnosis device is able to communicate with the ECUs via the relay device. The failure diagnosis device acquires various pieces of information from the ECUs and updates data within the ECUs.
However, in the conventional configuration, when relaying communication frames between the external device such as that described above and an on-board network, the relay device uses the routing table. Therefore, as shown in FIG. 1 for example, a message identifier and a port identifier are required to be stored for each type of message sent as a request from the failure diagnosis device to the ECU. A message identifier and a port identifier are also required to be stored for each type of message sent in response from the ECU to the failure diagnosis device.
Therefore, an enormous amount of content is stored in the routing table. A problem occurs in that the amount of content cannot be supported without the memory area of the relay device being increased. In addition, for example, the storage area of the relay device is required to be further increased and the routing table is required to be updated, not only for pre-existing external devices such as the failure diagnosis device, but also every time a new external device capable of communicating with the ECUs via the relay device is installed.
Therefore, a network system is desired that is capable of supporting communication between an on-board network and an external device without a storage area of a relay device being increased.